The present invention relates generally to integrated circuit (IC) designs, and more particularly to a semiconductor structure with a discontinuous material density for reducing eddy currents induced therein.
An eddy current is an electrical phenomenon caused by a moving magnetic field intersecting a conductor. It can occur in an IC chip, in which an inductor is placed on top of a semiconductor substrate. FIG. 1, for example, illustrates an inductor 100 placed above a semiconductor substrate 102. A magnetic field represented by magnetic flux 104 is induced by an electric current flowing through the inductor 100. The magnetic flux 104 cuts through the semiconductor substrate 102 underneath the inductor 100, and induces eddy currents 106 therein. The eddy currents 106 flowing in the semiconductor substrate 102 generates heat, and increases the power consumed by the inductor 104. Thus, it is desired that the induced eddy currents be reduced or eliminated.
Conventionally, the eddy currents 102 can be reduced by increasing the resistance of the semiconductor substrate 102. However, this approach may alter the electrical characteristics of the semiconductor substrate, thereby disturbing operations of the devices constructed on the substrate. Moreover, changing the resistance of the semiconductor substrate 102 requires additional processing steps. Thus, other solutions for reducing the induced eddy currents are needed.